Papermaking machine suction box with yieldably biased cover

ABSTRACT

A box structure which may be a suction box or blow box has a bottom wall, side walls, and an apertured cover and is mounted on a papermaking machine such that the cover is yieldably biased against a wire or felt carrying a paper web to dewater the web through the wire or felt or provide enhanced adherence of the web to the wire or felt. The entire box may be pivoted around a shaft and bracket and biased against the wire or felt by a spring connected to the bottom wall or the box may be immovable with a portion of the cover biased against the wire or felt by connection to a pivot arm and elastic tube.

March 14, 1972 5 NYKQPP 3,649,449

IAlI-IKMAKLNG MACHINE SUCTION BOX WITH YIELDABLY BIASED COVER Filed Jan. 27. 1970 2 Sheets-Sheet l 20% Fig. I

March 14, 1972 E. A. NYKOPP 3,649,449

PAPERMAKING MACHINE SUCTION BOX WITH YIELDABLY BIASED COVER 2 Sheets-Sheet 2 Filed Jan. '7, 1970 3,649,449 PAPERMAKING MACHINE SUCTION BOX WITH YIELDABLY BIASED COVER Erik Albert Nykopp, Tampere, Finland, assignor to y Tampella Ab, Tampere, Finland Filed Jan. 27, 1970, Ser. No. 6,234 Int. Cl. D21f 1/52 U.S. Cl. 162-365 11 Claims ABSTRACT OF THE DISCLOSURE A box structure which may be a suction box or blow box has a bottom wall, side walls, and an apertured cover and is mounted on a papermaking machine such that the cover is yieldably biased against a wire or felt carrying a paper web to dewater the web through the wire or felt or provide enhanced adherence of the web to the wire or felt. The entire box may be pivoted around a shaft and bracket and biased against the wire or felt by a spring connected to the bottom Wall or the box may be immovable with a portion of the cover biased against the wire or felt by connection to a pivot arm and elastic tube.

BACKGROUND OF THE INVENTION Field of the invention The present invention concerns a suction or blow box in paper machines and equivalent, in which the cover of the box has been placed against the surface of a wire or belt.

Description of the prior art Suction and blow boxes have been commonly employed in paper machines and equivalent for the purpose of dewatering the web through the wire or felt or for the purpose of making the web adhere to the surface of a wire or felt lapping a roll when this wire or felt is detached from the roll. Such devices belonging to previous art are rigid of their structure, and their perforated surface contacting the wire or felt, or their cover, consists of one piece and is level and integrally connected with the walls of the box, which in its turn is immovably mounted e.g. on the bed structures of the paper machine. A design of this kind has the drawback that irregularities in thickness which may occur in the web tend to damage the wire or felt, in particular if the web passes e.g. between a roll and a suction box or between a suction and blow box placed opposite each other.

The present invention eliminates the above-mentioned drawbacks and affords a suction or blow box in paper machines and equivalent that will appreciably reduce the damage of the wire and felts, thus prolonging the servicing interval.

SUMMARY OF THE INVENTION According to the invention the blow or suction box is employed in a paper machine with a plurality of rolls wherein means for mounting at least a part of the apertured cover is yieldably biased in order to accommodate such irregularities in the thickness resulting from imperfections as may occur in the material web.

The elastic movement of the cover or part thereof can be arranged to take place by several modes, such as e.g. substantially at right angles with reference to the wire or felt, or as a rotatory motion about an axis placed in the cross-machine direction under an endless flexible porous belt, e.g., a wire or felt, that is on the same side on which the suction or blow box is located, at a distance from nited States Patent O 3,649,449 Patented Mar. 14, 1972 the cover or from its yieldably biased part in the direction of wire or felt travel.

The yieldably biasing elements are either arranged to be located between the movable portion part of the cover and the bottom of the box, in which instance the box may be immovably mounted on the bed structures of the machine, or between the bottom of the box and the bed of the machine, in which instance it is advantageous if the entire box including its cover is yieldably biased.

In one advantageous embodiment, the yieldably biased part of the cover has been subdivided into a number of spaced apart independently yieldable bars extending in the direction across the box. The advantage with this arrangement is that the cover will not easily part from the wire or felt in its entirety even on encountering larger irregularities.

The yieldable biasing elements may be either helical springs or equivalent, and in particular they may be tubes or hoses with elastic walls which have been filled with air or liquid under pressure.

In one embodiment, the entire box has been yieldably biased to the bed of the machine, in which instance the cover has been integrally attached to the box.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 presents a sectional view, from the side, of one embodiment of a device according to the invention, in which part of the cover is yieldably biased, and

FIG. 2 shows, in sectional view from the side, another embodiment in which the entire cover and box are yieldably biased.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First embodiment In FIG. 1, the suction box 1 having walls 13a, 13b, 13c and 13d has been immovably mounted e.g. on the bed structures 16 of a paper machine. The suction Box 1 has two cover parts 2 and 2', of which one cover 2 has been attached to the rear wall 13a of the suction box 1 having a means 18 connected to the inside of the box to establish a pressure dilferential, e.g., suction source and the other, yieldably biased part 2' of the cover has been placed in the forward part of the suction box, close to its forward wall 13d. Means 18 is connected to a pressure differential source 20. The yieldably biased part 2' has been arranged to be turnable about a horizontal pin or shaft 5 fixed to the lug 6 on the rear wall 13a of the suction box 1 and directed across the direction of travel of the wire 3. The part 2 has ben connected with the shaft 5 by means of an extension 8 projecting downwardly from the part 2' and of the arm 7, to one end of which the extension 8 has been attached.

The lower part of the extension 8 rests upon an elastic tube 9, which has been loaded with compressed air. The tube 9, in its turn, rests on a raised structure 10 pointing upwardly from the bottom of the suction box 1, and consequently the part 2' is urged against the endless flexible porous belt, e.g., wire 3, which at this point is still backed by the roll 4. The material web travels between the wire 3 and roll 4 and follows along with the wire 3 when this is detached from the roll 4. The detachment is promoted by the vacuum prevailing in the suction box 1, causing the wire and web to be drawn against the covers 2 and 2' of the suction box. The apertures or slits in the cover components 2 and 2 have been indicated by the reference numeral 15 and cover components 2 and 2 provided with elastically yielding spaced bars 14a and 15a. By means of the adjustable screw 11, the upward movement of the part 2' can be restricted so that the pressure acting upon the wire 3 can be adjusted to have the desired magnitude.

Second embodiment The suction box shown in FIG. 2 differs from the first embodiment in the respect that the cover 112 consists of one piece and has been integrally attached to the suction box 111. Suction box 111 has side walls 113a, 1131;, 1131; and 113d. The elastic movement of the cover 112 with the elastically yielding spaced bars 14a is accomplished in this instance by arranging the entire suction box 111 to be yieldably biased. On the outer side of the wall 113a of the suction box a lug 117 has been placed, which has been arranged to be turnable about a pin or shaft 115 mounted by means of bracket 120 on the webforming machine 116a, in which connection in the leading part of the suction box, between the bottom wall 122 and the bed 116]) of the paper machine a spring 119 has been placed, which urges the cover 112 elastically against the wire 3, which is partially backed by the roll 4.

A device according to the invention is particularly advantageous when the opposite side of the wire or felt is backed by some machine component, in which case the wire or felt or wires or felts and the material web have to pass through a narrow gap.

In such circumstances the wires or felts are susceptible to damage in the event that there occur irregularities in the material web unless the width of the gap can be adjusted in accordance With the Web thickness. However, a device according to the invention may also be used in the case that the upper surface of the web is free and unsupported.

What is claimed is:

1. In a paper machine of the type comprising a bed structure, a roll rotatably mounted on the bed structure, and an endless, flexible porous belt supported for movement in a closed path defined in part by the roll to transport a material web, the combination of a box structure comprising a bottom wall, and side walls extending from said bottom wall; an apertured cover for said box structure;

means communicating with the interior of said box structure to establish via the apertures of said cover a pressure differential between the surface of the belt against which said cover is disposed and the opposite surface of the belt, to provide air flow through the material web supported by the belt, and

mounting means cooperating with said box structure and supporting at least a portion of said cover against a surface of the belt for movement toward and away from the belt in order to accommodate irregularities in the material web, said mounting means including yieldable means biasing said portion of said cover toward the .belt.

2. The combination defined in claim 1, wherein said at least a portion of said cover comprises a plurality of spaced apart independently yieldable bars.

3. In a paper machine of the type comprising a bed structure, a roll rotatably mounted on the bed structure, and an endless, flexible porous belt supported for movement in a closed path defined in part by the roll to trans port a material web, the combination of a box structure comprising a bottom wall, and side walls extending from said bottom wall; an apertured cover for said box structure;

means communicating with the interior of said box structure to establish via the apertures of said cover a. pressure differential between the surface of the belt against which said cover is disposed and the opposite surface of the belt, to provide air flow through the material web supported by the belt, and mounting means for supporting said box structure and cover on the bed structure with said cover disposed 4 against a surface of the belt, said mounting means including:

means connected to one of said side walls for pivoting said box for movement toward and away from the belt in order to accommodate irregularities in the material web, and yieldable means connected to said bottom wall for biasing said portion of said box and cover toward the belt.

4. The combination defined in claim 3, wherein said means connected to said side wall for pivoting said box for movement toward and away from the belt constrains the same to move at substantially right angles to the belt.

5. The combination defined in claim 3, wherein said yieldable means is connected between said bottom Wall of said box structure and the bed structure.

6. In a paper machine of the type comprising a bed structure, a roll rotatably mounted on the bed structure, and an endless, flexible porous belt supported for movement in a closed path defined in part by the roll to transport a material Web, the combination of a box structure comprising a bottom wall, and side walls extending from said bottom wall, said box being immovably mounted;

an apertured cover for said box structure;

means communicating with the interior of said box structure to establish via the apertures of said cover a pressure differential between the surface of the belt against which said cover is disposed and the opposite surface of the belt, to provide air flow through the material web supported by the belt, and

mounting means cooperating with said box structure and supporting at least a portion of said cover against a surface of the belt for movement toward and away from the belt in order to accommodate irregularities in the material web, said mounting means including yieldable means biasing said portion of said cover toward the belt.

7. The combination defined in claim 6, wherein said at least a portion of said cover is movable relative to said box structure, and

said yieldable means is interposed between said at least a portion of said cover and said bottom wall of said box structure.

8. The combination defined in claim 6, wherein sald means supporting at least a portion of said cover for movement toward and away from the belt comprises a support mounted on the bed structure and spaced from the belt on the same side thereof as said box structure, and an arm having one end connected to said support for pivotal movement about an axis transverse to the direction of travel of the belt, the other end of said arm being connected to said at least a portion of said cover, 7 said support being spaced from said at least a portion of said cover generally in the direction of travel of the belt. 9. The combination defined in claim 6, wherein said means supporting at least a portion of said cover for movement toward and away from the belt comprises an arm extending within said box structure at least generally in the direction of travel of the belt, one end of said arm being connected to said at least a portion of said cover, the other end of said arm being connected to said box structure for pivotal movement about an axis transverve to the direction of travel of the belt.

10. The combination defined in claim 6, wherein said cover comprises two separate portions, one of said portions being disposed in engagement with the surface of the belt in a location where the belt is backed up on its opposite surface by a part of the paper machine, only said one portion of said cover being supported for movement toward and away from the belt.

11. The combination defined in claim 10, wherein the portion of the belt engaged by said one portion of said cover is backed up by the roll, the other of said portions of said cover being spaced from the roll in the direction of travel of the belt.

References Cited UNITED STATES PATENTS 1,231,717 7/1917 Davies 162-365 5 REUBEN FRIEDMAN, Primary Examiner R. H. TUSHIN, Assistant Examiner U.S. Cl. X.R. 

